The present invention relates generally to continuous motion apparatus for decorating cylindrical containers, and relates more particularly to simplified apparatus of this type that does not require a deco chain for conveying decorated containers to a curing oven. It more specifically improves the transfer system between the can decorating and inking mandrel wheel and the curing oven for the decorated cans.
In high speed continuous motion equipment that decorates cylindrical containers (cans) for beverages and the like, decorated containers having wet decorations thereon were often off-loaded onto pins of a so-called deco chain that carries the containers through an ink curing and drying oven. Examples of this type of decorating equipment are disclosed in U.S. Pat. No. 5,183,145 which issued Feb. 2, 1993 to R. Williams et al., entitled Apparatus And Method For Automatically Positioning Valve Means Controlling The Application of Pressurized Air To Mandrels On a Rotating Carrier, and in U.S. Pat. No. 4,445,431 which issued May 1, 1984 to J. Stirbis entitled Disk Transfer System. Incorporated herein by reference are teachings of U.S. Pat. Nos. 5,183,145 and 4,445,431, as well as teachings of prior art patents referred to therein.
Over the years, production speeds of continuous motion can decorators have increased, now surpassing 1,800 cans/min., and it is desired to increase that speed still further. As speeds have increased, problems of unloading cans with wet decoraticins onto deco chain pins as well as problems with deco chains per se, have become more apparent and bothersome. These problems include excessive noise and can damage because of engagement between metal cans and metal pins. Not only are long deco chains expensive, but because they are constructed of so many parts there is a tendency for the chains to wear out and break down when operated at very high speeds.
Because of the foregoing problems, where feasible, decorated containers, especially those constructed of ferrous material are carried through curing ovens on belts rather than on the pins of a deco chain. Examples of such type of equipment using belts for carrying cans through curing ovens are found in U.S. Pat. No. 4,771,879 which issued Sep. 20, 1988 to F. L. Shriver for a Container Transfer System and in U.S. Pat. No. 5,749,631 which issued May 12, 1998 to R. Williams for a Dual Can Rotating Transfer Plate To Conveyor Plate. The teachings of U.S. Pat. Nos. 4,771,879 and 5,749,631, as well as teachings of prior art patents referred to therein, are also incorporated herein by reference.
In the can decorating apparatus of U.S. Pat. No. 4,771,879 cans are decorated, i.e., inked, on their surface while they are on mandrels that are mounted along the periphery of a mandrel wheel and the cans extend axially forward from the wheel. The decorated cans are transferred from the mandrels of the rotating mandrel wheel to a rotating wheel-like first transfer conveyor, are then further transferred from the first conveyor to the surface of a wheel-like second transfer conveyor and are thereafter transferred to a belt conveyor which carries the containers with still wet decorations thereon to and through a curing oven which cures the applied decorations. Cans conveyed by the second transfer conveyor project radially with respect to the rotational axis of the second transfer conveyor. While this arrangement avoids use of a deco chain, the second transfer conveyor of U.S. Pat. No. 4,771,879 is an expensive structure that is constructed of many parts, and there must be very close coordination between operation of the first and second transfer conveyors. Further, rotational axes for the two transfer conveyors are oriented transverse to one another resulting in inefficient utilization of space.
According to the invention disclosed in U.S. Pat. No. 5,749,631, cans with wet decorations thereon are transferred from the mandrel wheel to a first transfer conveyor wheel, then to a second transfer or takeaway conveyor wheel, and thereafter to a conveyor belt. The most obvious differences between U.S. Pat. Nos. 4,771,879 and 5,749,631 is that in the latter patent, the rotational axes of the transfer conveyors are oriented parallel to each other and are radially offset, and the second transfer conveyor has a simplified construction because cans conveyed by that conveyor project axially, parallel to the rotation axis of the second transfer conveyor. This is made possible by the second transfer conveyor including a rotating plate and a stationary suction manifold disposed behind the plate.
The manifold has an open side that is covered by a perforated portion of the plate that rotates past the open side of the manifold. The reduced pressure in the suction manifold generates suction at the perforations.
Cans travel in a single row around the mandrel wheel and are spaced relatively further apart to enable their decoration by the blankets of the blanket wheel. Hence, the decorated cans travel in a single row onto the first transfer conveyor from the mandrel wheel. The relatively larger spacing between cans on the mandrel wheel is not economical for space usage or for maximizing production in the curing oven. As the first transfer conveyor rotates past the mandrel wheel, the cans are rearranged into two rows on the first transfer conveyor. Rotating the first transfer conveyor slower than the mandrel wheel spaces the cans closer together on the first conveyor. Both of these expedients use space more economically. Then cans arranged in two rows on the first transfer conveyor are transferred to the rotating plate of the second transfer conveyor. Open ends of the cons engage a main planar surface of the plate at areas of the plate where perforations through the plate are arrayed over the suction manifold in two circular rows about the rotational axis of the plate as a center. The suction force at the plate perforations draws the cans rearward off the first conveyor toward the rotating plate of the second conveyor while the cans pass over the manifold. The influence of manifold suction on the cans is reduced when the closed ends of the cans rotate to and engage a vertical flight of a moving perforated belt conveyor, and the cans are thereafter held on the belt by suction forces at the perforations of the belt conveyor. The belt conveyor may carry the cans through a curing oven or transfer them to another conveyor that passes through the curing oven.
In order to rearrange the traveling cans carried by the rotating first transfer conveyor from a single row array as the cans are received by the first conveyor to a two row array as the cans are about to be delivered to the rotating plate of the second transfer conveyor, a somewhat complicated mechanism is provided on the first conveyor of the ""631 patent. The mechanism operates alternate ones of the cans that have been received by the first transfer conveyor to move radially inward toward the rotational axis of the first transfer conveyor before the cans reach the second conveyor.
Shifting cans radially on a rotating transfer conveyor, by using a cam for guiding the cans into two rows on the conveyor, is shown in U.S. Pat. No. 5,183,145. But this patent is not concerned with so positioning cons for transfer between a first and a second conveyor that the cans will be in selected correct locations on the second conveyor, and the present invention is concerned with accomplishing that. The same comment applies to the single transfer conveyor shown in U.S. Pat. No. 5,231,926.
Instead of utilizing the prior art complicated mechanism for rearranging the cans on the first transfer conveyor from a single row array to a two row array on the second conveyor, in the instant invention, on the first transfer conveyor the cans move only in a single row arrangement along a path of uniform radius about the rotational axis of the first transfer conveyor as a center. The rotation speeds of the mandrel wheel and of the first transfer conveyor are coordinated so that their peripheral speeds are set for spacing the cans transferred in a single row arrangement to the first conveyor at a useful, economical spacing on the first conveyor that may be shorter than the spacing between the row of cans on the decorating mandrel wheel. For example, the rotation speed of the rows of cans on first conveyor may be slower than the rotation speed of the row of cans rotating on the mandrel wheel. The cans are preferably secured at their bottom ends on the first conveyor by suction cups. The cans then travel in their row around the first conveyor to a transfer zone to be transferred to the second take-away conveyor.
At the next transfer zone, the cans are delivered to the rotating plate of the second takeaway conveyor. The circular path for the single row of cans carried by the first transfer conveyor crosses over obliquely and momentarily overlaps and is axially spaced away from two concentric outer and inner, circular suction applying tracks formed in the rotating plate of the second transfer conveyor. The tracks are formed about the rotation axis of the second transfer conveyor. As a first plurality of alternate cans in the row along the path of cans on the first conveyor overlap the outer track of the second conveyor, the first plurality of alternate cans are released from the circular path on the first transfer conveyor and engage the second transfer conveyor, being drawn to the second conveyor and held thereon by a suction force applied at the outer track. The remaining second plurality of alternate cans on the circular path on the first transfer conveyor are not released from the first transfer conveyor at the outer track of the second conveyor, but are instead rotated further until each second of the second cans on the path of the first conveyor overlaps the inner track of the second conveyor. The remaining second alternate cans are there released from the first transfer conveyor to be held on the second conveyor by a suction force applied at the inner track. Now the cans on the tracks of the second takeaway conveyor are in two rows.
The rotation speeds of the first and second conveyors are selected so that the speed of cans on the single row of the first conveyor and the speed of the cans at the inner and outer tracks of the second conveyor achieve desired spacing and separation of the cans on the inner and outer tracks of the second conveyor for economical operation, i.e., the more closely spaced the cans are, the greater is the rate of production for any given speed of the second conveyor and of the later transfer belt.
From the second conveyor, the two rows of cans are again transferred to a usually upward moving flight of a belt conveyor which carries the cans downstream toward a curing oven in two rows of cans. The belt, like the transfer conveyors, holds the cans preferably by suction, so that as the second conveyor is rotated so that cans approach the belt, the suction on the cans at the second conveyor is released and suction is applied through the belt to draw the cans to and transfer the cans to the belt. The speed of the belt is coordinated with the rotation speed of the tracks on the second conveyor to optimally space the cans on the belt conveyor. For example, the speed of the belt conveyor is below the rotation speed of the tracks to space the cans in the two rows on the belt to be as close as practical to each other as they are conveyed through the curing oven, and typically much closer together than the cans in the single row on the mandrel wheel and around the first transfer conveyor and closer together than the cans on the two tracks of the second conveyor.
Each of the first transfer conveyor, the second takeaway conveyor and the belt conveyor draws the cans to them and secures the cans to them preferably by suction applied to the cans, or optionally by magnetic attraction if the cans are ferrous metal. As a result, various provisions are made to insure that the cans are correctly positioned on all of those conveyors. The suction or magnetic force applied in each case and cups for holding the ends of the cans on the first conveyor are selected to position the cans correctly. But at the second conveyor and the belt conveyor where there is no element positively mechanically positioning the cans, some cans may be transferred to be off their desirable location or may fall away completely. It is recognized that an object following a circular, curved or otherwise profiled pathway is traveling along a tangent to that pathway at each instant. If a transfer involves a can being redirected obliquely across a tangent to the pathway on which it is then moving, there are dangers that the can may shift laterally off the selected path due to its inertia or that it may leave the desired path entirely where cans are held in position by suction or magnetic attraction.
In this apparatus, each transfer between conveyors occurs by movement of a axially from one of the conveyors in sequence on the path to another conveyor. There may be instances when the can is not in mechanical contact with either of the conveyors between which it is transferring during the instant of transfer and especially if at the time of transfer, the can is to be directed in a pith off the tangent to the pathway on which the can had just been traveling, the can may become mispositioned on the succeeding conveyor to which it is being transferred. Therefore, at each transfer between conveyors, the path of the cans on the preceding conveyor is along a straight pathway or is along a tangent to a curved pathway, such that the tangents to the path of the can on the conveyor which it is leaving is the same and parallel to a tangent on the path on the succeeding conveyor to which the can is being transferred. Implementation of this aspect of the transfer has enabled the operating speed of the can decorator to be increased. In contrast, in an arrangement where a tangent to the pathway from which the can is leaving is not the same as nor parallel to the tangent to the pathway to which the can is being transferred, the inertia of the can may cause the can to move off the desired tangential direction pathway of the transferee conveyor to which the can is being transferred. This has placed a limit on the speed of operation of the can decorator to ensure that can inertia does not move the cans off the desired transferee path. But where the tangents to the paths of the transferor and transferee conveyors at the can transfers are parallel, the inertia of a can will not shift the can off the desired transferee pathway before the can has been securely transferred to the transferee conveyor in the path. This has enabled a significantly higher operating speed for the can decorator.
To apply the foregoing principle to the transfer arrangement where the single row of cans on the first transfer conveyor is transferred to two concentric tracks on the second conveyor, the pathway of a plurality of the cans on the first conveyor must be adjusted.
The single row of cans on the first conveyor would normally cross over and above the outer track on the second conveyor and intersect the inner track of the second conveyor. Preferably, alternate cans in a first plurality of cans on the first conveyor are delivered to the inner track, while the next alternate cons in a second plurality of the cans on the first conveyor are delivered to the outer track, then a first can to the inner track, etc. The first and second conveyors, the path of the cans on the first conveyor, and the inner and outer tracks of the second conveyor are all so placed that the path of the first conveyor is tangent to the path of the inner track of the second conveyor and at the tangent location, the first plurality of cans are transferred, by the suction applied at the second conveyor, from the first conveyor to the second conveyor.
However, this same arrangement of the path of the cans on the first conveyor and of the tracks of the second conveyor causes a tangent to the path of the cans on the first conveyor to obliquely intersect a tangent to the outer track on the second conveyor, and those tangents are not parallel where the path on the first conveyor and the outer track on the second conveyor intersect. The cans to be transferred to the outer track are transferred at that intersection. At that transfer, the path each such can is traveling must be instantly redirected to the tangent to the outer track of the conveyor from the then path which is oblique to the tangent to the path on the first conveyor. At slower operating speeds, a sudden redirection of the cons at a transfer to the outer track of the second conveyor usually does not cause those cans to be displaced on the second conveyor. But as operating speeds increase, e.g. up to and above 2,000 cans per minute, the rotation speeds of the first and second transfer conveyors increase such that sudden redirection of the path of the cans at the outer track of the second conveyor may cause a can to shift out of its desired position at the outer track, or worse, may cause the can to separate entirely from the second conveyor before it is held to the second conveyor by the suction at the outer track. This could limit the maximum operating speeds.
According to a modified embodiment of the present invention, selected ones, e.g., the alternate second plurality of cans in the single row of cans that are transferred in a single row from the mandrel wheel to the first transfer conveyor, are shifted radially inwardly on the first transfer conveyor as they are rotated to approach the transfer from the first conveyor to the outer track of the second conveyor, so that at the transfer of the second plurality, and particularly alternate cans from the first conveyor to the outer track of the second conveyor, the radius on the first conveyor of the path of the cans to be transferred to the outer track is shortened so that the tangent to the path of the cans on the first conveyor overlaps and is parallel to the tangent of the outer track on the second conveyor where the transfer takes place. This expedient assures that the first plurality of alternate cans being transferred from the first conveyor to the inner track and the second plurality of cans being transferred from the first conveyor to the outer track are transferred where the tangents to their respective paths on the first conveyor are parallel to the tangents to their respective paths on both the inner and outer tracks of the second conveyor. The above described limit on the operating speed of the transfer arrangement described above is thereby eliminated and more rapid can decoration may be expected.
The further transfer of cans from the two rows of the second transfer conveyor to the belt is readily accomplished because the path of the belt at the transfer from the second conveyor to the belt may be selected so that the belt is moving parallel to the tangent to each of the tracks on the second conveyor at the transfer to the belt.
Accordingly, the primary object of this invention is to provide simplified apparatus that conveys cans from a continuous motion high speed decorator through a curing oven without placing the cans on pins of a deco chain.
Another object is to provide apparatus of this type in which there are partially overlapping first and second transfer conveyors that rotate on laterally offset parallel horizontal axes, with the second transfer conveyor including a rotating plate having a planar surface that receives cans from the first transfer conveyor with the open ends of the cans directly engaging a planar surface which is perpendicular to the rotational axis of the second transfer conveyor.
Yet another object is to transfer cans on a single circular path of a first rotating conveyor to first and second concentric circular tracks of a second rotating conveyor.
A further object is to operate the transfer conveyors to minimize spacing between cans for economical operation.
Another object is to increase the rate of can production and thus the speed, while maintaining positive control over the motion of the cans as they are transferred from the decorator mandrel wheel, over the transfer conveyors and to a curing oven.
A still further object is to provide apparatus of this type in which linear speed for containers on the second transfer conveyor may be less than the linear speed for the containers on the first transfer conveyor.
Still another object is to provide apparatus of this type in which the cans are transferred directly from the planar surface to a moving vertical flight of a belt conveyor.
A further object is to provide. apparatus of this type having operating principles that enable suction as well as magnetic forces to be utilized for holding ferrous containers.
Yet another object is to provide apparatus of this type wherein cans are held by suction devices that include very shallow flexible suction cups with stiff backups closely spaced from the flexible cups and with the cups being so large that they remain totally outside of the inverted domes that are at the closed ends of the cans.